HAProxy apparently not forwarding correctly - reverse-proxy

Question

I'm using this HAProxy config file:
defaults
mode http
frontend main
bind *:80
use_backend drewgrosscom if { hdr(host) -i drewgross.com }
use_backend drewgrosscom if { hdr(host) -i www.drewgross.com }
use_backend drewgrosscom if { hdr(host) -i drewallyngross.com }
use_backend drewgrosscom if { hdr(host) -i www.drewallyngross.com }
use_backend idoor if { hdr(host) -i idoor.drewgross.com }
backend drewgrosscom
server s1 127.0.0.1:8000
backend idoor
server s3 127.0.0.1:8002
All of the things that forward to the drewgrosscom backend work fine, but visiting idoor.drewgross.com gives me nothing. The server is definitely running and serving on port 8002, because I can visit either drewgross.com:8002 or <my-servers-ip>:8002 and see the thing I expect to see. What am I missing here?

Answer 1

By default, HAProxy works in tunnel mode. That means, it will inspect only the first request in a connection, no matter if it's a keep-alive connection or not. After the request has been dispatched, all further communication of this specific TCP connection will then be send to the selected backend server of the first request.
To mitigate this, you could either completely disable keep-alive
option httpclose
or enable keep-alive between the client and HAProxy but to disable it between HAProxy and the backend server
option http-server-close
A third (incomplete and still very much work-in-progress) option available in HAProxy 1.5-dev20 or newer is full keep-alive support with
option http-keep-alive
You have to use one of these options to analyze (and switch) all HTTP requests. For a production site, I'd currently recommend option http-server-close.